1. Field of the Invention
This invention relates generally to a spacecraft module including an internal "eggcrate" structural layout, and a method of converting a spacecraft deorbit propulsion module to more complex spacecraft modules to be used in connection with various types of space vehicles for different missions, such as a crew return vehicle, a crew transport vehicle, a refueling tanker, a logistics re-supply module, a space station reboost module, etc.
2. Discussion of the Related Art
Spacecraft and their associated propulsion stages are typically designed for a single use and for performing a single type of space mission. Thus, the design of the spacecraft, including the size, shape, payload, avionics equipment, propulsion capacity, and electrical power storage and regeneration capacity, are tailored for the intended space mission without concern for satisfying any other mission or operational requirements. For example, the known Centaur upper stage is designed to have a certain propulsive capability for a certain class of missions and a certain class of payloads. Its ability to be adapted to other types of missions for different classes of payloads once it is designed is very limited. The advantage in this type of approach is that the spacecraft is designed to be the most efficient and least expensive way to meet the requirements for a particular mission. Accordingly, providing for different types of space missions has generally required independent design and assembly of entirely different types of space vehicles, each designed for performing its own specific space mission. This overall approach is both extremely costly and time consuming in the long run to satisfy all types of missions.
It has been proposed in the art to design a multi-mission modular spacecraft that can be used for multiple mission types to help reduce the costs involved in multiple mission space programs. U.S. Pat. No. 4,880,187 issued to Rourke et al., and assigned to the assignee of the instant application, attempts to satisfy the need for a multiple spacecraft that can be adapted to different mission requirements. The '187 patent discloses a multipurpose modular spacecraft that includes a fully integrated short-range space vehicle designed to accept and interface with one or more self-contained modular propulsion units of different sizes and different propulsion capacities in accordance with the requirements of a particular space mission. The short-range vehicle includes a relatively large open-sided chamber in the rear axial face of the vehicle that accepts a long-term propulsion module. Therefore, the short-term modular propulsion units can be readily removed, and the long-term propulsion module can be inserted for longer space missions.
The multipurpose modular spacecraft disclosed in the '187 patent does satisfy a need for a single spacecraft that is usable for different mission types. However, the multipurpose spacecraft is initially designed for both short-term and long-term missions, and thus includes the capacity for both types of missions at the lowest design level. Because it is initially designed to meet several types of mission requirements, the modular spacecraft of this invention is relatively complex and costly to implement, even for low-end space missions.
The need for multiple types of space missions having different requirements is apparent from the requirements necessary to operate a space station. Several countries are currently collaborating on the design, development, deployment and maintenance of an international space station (ISS). One purpose of the multigovemment involvement in development of the ISS is to better account for the extreme costs involved in such a project. Different countries have been assigned different aspects of the ISS to develop the finished product. Some of the different spacecrafts required for the operation of the ISS includes a crew return vehicle (CRV), which is an emergency life boat for crew members currently stationed on the ISS. A deorbit propulsion module (DPM) having four degrees of freedom is necessary for on-orbit attitude control and deorbit impulses required to bring the CRV back to Earth from the ISS. The DPM derived vehicle can also provide reboost and attitude control of the ISS to maintain a desired orbit. Additionally, a crew transport vehicle (CTV) is required for transporting crew members to the ISS and back to Earth for crew rotation. The CTV requires a propulsion module having six degrees of freedom. Additionally, a logistics resupply vehicle (LRV) is required for unmanned delivery of cargo and other payload to the ISS. A refueling tanker is also necessary to supply fuel to the ISS when needed. Both the LRV and the refueling tanker would require a propulsion module or some form of propulsive stage. Some of the space vehicles required for these missions can be launched from Earth by an expendable launch vehicle (ELV), such as the Atlas, Delta, or Ariane V, or be launched from Earth in the shuttle orbiter. Each of the various space vehicles for different missions have different requirements and mission needs.
Because of the multigovernmental involvement, the political backdrop and the economic conditions surrounding the participation of various countries is uncertain. It has been recognized by the current inventors that a basic core propulsion vehicle could be used and modified to provide the various support functions in connection with the ISS, as well as other space missions. By providing this basic core vehicle, the contributions from other countries may not need to be relied on, and the expense of the project can be limited.
There exists a need for an improved spacecraft designed for rapid, easy and safe adaptation for performing a wide variety of different space missions in a cost conscious manner. It is therefore an object of the present invention to provide an evolvable propulsion module that can be modified to provide various mission functions, such as a propulsion module for CRVs, CTVs, logistics resupply vehicles, ISS refueling and ISS reboost and attitude control.